Control system



June 15, 1937. w. GlLLE 2,083,780

' CONTROL SYSTEM Filed Sept. 24, 1934 HUMIDITY RESPONSIVE VARIABLE RESISTANCE Jwuemtcw Willis H Gille Patented June 15, 1937 UNITED STATES CONTROL SYSTEM Willis H. Gille, St. Paul, Minn.,' assignor to Minneapolis-Honeywell Regulator Company, Minneapolls, Minn, a corporation of Delaware Application September 24, 1934, Serial No. 745,374

6 Claims.

This invention relates to control mechanisms in which small and delicate changes in a condition are amplified to operate devices requiring a relatively stronger force and has particular utility in humidity control devices wherein the changes in the condition are small and delicate and not suflicient to operate the humidity control device directly.

An object of this invention is to provide a more sensitive control mechanism wherein small and delicate changes in a condition acting thereon which are insuflicient to operate a control device directly are amplified to operate said control device.

Another objectof this invention is to provide a control mechanism wherein an ofi and on control is provided at the command of a small change in resistance of an active element of the variable resistance type.

A further object is to provide a control mechanism wherein voltage changes and ambient temperature changes are compensated to nullify their effect. c

A still further object is to provide a control mechanism wherein the Control point may be adjusted from a remote position.

More specifically, another object is to provide a humidity control system wherein small and delicate changes in resistance of a humidity responsive variable resistance are amplified to provide an oif and on control for a mechanism to control the humidity.

Other objects and advantages will become apparent to those skilledin the art by reference to the accompanying specification and drawing in which there is shown a diagrammatic view of my control system, preferably applied to a humidity control.

The control system is of general utility and may beused in connection with practically any system and may be responsive to practically any condition but for purposes of illustration and not for limitation it is shown as applied to a humidity control wherein Hiis a water pipe delivering a spray of water to the space, the humidity of which is to be controlled. Located in the pipe i0 is an open and shut valvel l operated from full open position to full closed position andvice versa by a double solenoid which valve and solenoid may take the form disclosedin the patent to George D. Bower No. 1,861,046, filed May 24th, 1928, and patentedMay-Blst, 1932.

The energyfor operating the double solenoid l2 is-obtained from line wires l3 and I l, line wire it being made flexible as at it and being soldered to a contact arm l6. Line wire I l extends directly to the double solenoid. The C011? tact arm I6 is adapted tov selectively engage a contact I! or a contact l8 which contacts are connected by wires I9 and 20 respectively to the 5 double solenoid l2. I

When the contact arm it engages the contact H, the double solenoid I2 is energized to close the valve H and when the contact arm 06 engages the contact l8, the double solenoid i2 is 10 energized to, open the valve it.

The contact arm I6 is operated by a double heat responsive device which consists of a bimetallic arm 24 secured at one end to a support 25 and a second bimetallic arm 22 secured at one 15 end thereof to the other end of the first bimetallic arm 24 by means of a pin 23. The lower end of the bimetallic arm 22 is connected to the contact arm it. As the bimetallic element 28 is heated, it being secured to the support 25, the element will bend or flex in a counter-clockwise direction thereby tending to move the contact arm I 6 towards the contact it. When the bimetallic element 22, being secured at its upper end to the pin 23, is heated, it bends or flexes 25 in a clockwise direction, tending to move the contact arm it towards the contact ll. It will be noted at this point that theelements 22 and 2 3 when heated operatein opposite directions so that ambient changes in temperature of the 30 surrounding atmosphere have no effect upon this portion of the instrument.

The bimetallic heat responsive element 22 is heated by a heating element 21 while the bimetallic heat responsive element 24 is heated by a 35 heating element 28. These heating elements 21 and 28 obtain their energy from line wires 30 and 3| connected to theprimary-33 of a step down transformer 32. The secondary 34 of the transformer 32 is connected by means of a wire 40 35 to, one end of the heating element 28. The

other end of the heating element 28 is connected I Starkins N0. 1,694,107 filed March 24th, 1926'and patented December 4th, 1928. Such a variable 4i is connected to the wire which in turn is connected to the secondary 34 of transformer 32. The other wire 42 of the variable resistance is connected by a wire 44 to one end oi. the heating element 21 while the other end of the heating element 21 is connected by a wire 43 to that end of heating element 23 which is connected to the wire 35.

The resistance 43 is varied by moisture permeating the cotton insulation of the wires 4| and 42 so that greater moisture lowers the resistance between wires 4| and 42' and less moisture increases the resistance therebetween the amount of resistance varying exponentially with respect to the vapor content or relative humidity of the atmosphere in which .the device is placed.

The circuit for operating the heat responsive element 24 is completed through the secondary 34 of the transformer 32, wire 3 5,heating element 23, wire 33, adjustable contact 31, resistance coil 33.wire32 and'wire 44. I

The circuit for operating the heat responsive element 22 is completed through secondary 34,

wire 3!, wire 45, heating element 21, wire 44, conduction through the insulating means between wires 4i and 42 of the variable resistance 43, and the wire 43. I

The adjustable resistance 33 determines the amount of heat given oiI by the heating element 23 and may be located at a point remote from the rest of the structure. -By increasing the resistance 34, the amount of heat given of! by the heating element 22 is reduced and by decreasing the resistance 34, the amount of heat given oil by the heating element 23 is increased. For a given setting of the resistance 33, the heat given 012 by the heating element 23 will be substantially constant except for slight changes in line voltage thereby urging the contact arm it towards the contact I. with a substantially constant force.

The heat given ofif by the heating element 21 is inversely proportional, in an exponential manner, to the amount of resistance in the resistance 43. As the humidity increases, the resistance of the variable resistance 43 decreases and permits heating element 21 to give of! more heat to the heat responsive element 22 to tend to urge the contact arm ii towards the contact l1.

Due to the fact that the heating elements 21 and 23 cause the heat responsive elements 22 and 24 respectively to operate in opposite directions, and since both heating elements 21 and 23 receive their energy from a common source, the lines 33 and 3i, any fluctuations in the line voltage are compensated and nullified.

Assume that the parts are in equilibrium and are in the position shown in the drawing, heating element 23 tends to urge the contact arm it towards the contact .i3 and heating element 21 tends to urge the contact am It towards the contact i1. when the humidity decreases, the resistance in the variable resistance 43 increases and causes the heat given ofl by the heating element 21 to decrease whereby the contact arm it will engage the contact i3 to energize the double solenoid i2 to open the valve which supplies more water to the atmosphere and brings the humidity up to normal and allows the parts to resume their equilibrium positions as shown in the drawing. Assume that the humidity increases, the resistance 43 decreases, allowing the heating element 21 to develop more heat to fiex the heat responsive element 22 which causes contact arm I to engage contact l1 totenergise the double solenoid i2 to close the valve ii to decrease the amount of water vapor in the air and bring the parts back to equilibrimn again as shown in the drawing.

From the above, it is seen that I have provided a 'more sensitive control mechanism wherein small and delicate changes in conditions acting thereon which are-insufiicient to operates control device directly are amplified to operate said control device.

while one embodiment oi this invention has been shown and described, it is obvious that many modifications may be apparent to one skilled in the art and consequently, this invention is to be limited only by the scope of the appended claims.

I claim: I

1'. In a control of the character described, a variable resistance responsive to changes in humidity, a solenoid operated valve mechanism tocontrol the humidity, an oil and on switching mechanism, a circuit connecting said on and on switching mechanism and said solenoid operatedvalve mechanism to open and close said valve mechanism in response to said switching mechanism, means to operate said circuit connecting said source andsaid heating element to constantly urge said switching mechanism in one direction, a second heating element controlling said second heat responsive element and a second circuit connecting said source, said humidity responsive variable resistance and said second heating element to urge said switching mechanism in the other direction according to changes in humidity acting on said variable resistance whereby both of said heating elements are arranged to compensate for voltage changes in said source and an adiustable resistance in said first circuit to adjust the heating efiect oi said first heating element to make said control system responsive to greater or less conditions of humidity.

2. In a control system of the character described, a variable resistance responsive to changes in humidity, a solenoid operated valve mechanism to control the humidity, an ofi and on switching mechanism, a circuit connecting said oil! and on switching mechanism and said solenoid operated valve mechanism to open and close said valve mechanism in response to said switching mechanism and means to operate said switching mechanism according to changes in resistance in said humidity responsive variable re element to constantly urge said switching mechanism in one direction, a second heating element controlling said second heat responsive element and a second circuit connecting said source,

said humidity responsive variable resistance and said second heating element to urge said switching mechanism in the other direction according to changes in humidity acting on said variable resistance whereby b oth oi said heating elements .10 are arranged to compensate for voltage changes in said source.

3. In a control system, a variable resistance responsive to changes in a condition, an electrically operated control mechanism to control said 15 condition, an off and on switching mechanism, a circuit connecting said switching mechanism and said electrically operated control mechanism to operate said control mechanism in response to said switching mechanism, means to operate 20 said switching mechanism according to changes 01' resistance in said variable resistance comprising a heat responsive element secured at one end and acting in one direction, a second heat responsive element secured at one end to the other 25 end oi said first heat responsive element and at the other end to said switching mechanism and acting in the opposite direction whereby ambient temperature changes are compensated, a source of energy, a heating element controlling said first 30 heat responsive element, a circuit connecting said source and said heating element to constantly urge said switching mechanism in one direction, a second heating element controlling said second heat responsive element and a sec- 35 ond circuit connecting said source, said second heating element and said variable resistance to urge said switching mechanism in the other direction according to changes in the condition acting on said variable resistance whereby both of said heating elements are arranged to compensate ior voltage changes in said source and an adjustable resistance in said first circuit to adjust the heating efl'ect of said first heating element to make said control system responsive to greater or less changes in the condition.

4. In a control system, a variable resistance responsive to changes in a condition, an electrically operated control mechanism to control said condition, an oil and on switching mechanism, a circuit connecting said switching mechanism and said electrically operated control mechanism to operate said control mechanism in response to said switching mechanism, and means to operate said switching mechanism according to changes or resistance in said variable resistance comprising a heat responsive element secured at one end and acting in one direction, a second heat responsive element secured at one end to the other end or said first heat responsive element and at the other end to said switching mechanism and acting in the opposite direction whereby ambient temperature changes are compensated, a source of energy, a heating element controlling said first heat responsive element, a circuit connecting said source and said heating element to constantly urge said switching mechanism in one direction, a second heating element controlling said second heat responsive element and a second circuit connecting said source, said second heating element and said variable resistance to urge said switching mechanism in the other direction according to changes in the condition acting on said variable resistance whereby both of said heating elements are arranged to compensate for voltage changes.

5. In a control system, the combination of, a variable resistance responsive to changes in a condition, a mechanism to be operated, means to operate said mechanism according to changes of resistance in said variable resistance comprising a heat responsive element secured at one end and acting in one direction, a second heat responsive element secured at one end to the other end of said first heat responsive element and at the other end to said mechanism and acting in the opposite direction whereby ambient temperatures are compensated, a source 01' energy, a heating element controlling said first heat responsive element, a heating element controlling said second heat responsive element, and connections between said source, said variable resistance and said heating elements whereby said mechanism is moved in accordance with changes in the condition varying the resistance.

6. In a control system, the combination of, a variable resistance, a mechanism to be operated, means to operate said mechanism according to changes of resistance in said variable resistance comprising a heat responsive element secured at one end and acting in one direction, a' second heat responsive element secured at one end to the other end 01' said first heat responsive element and at the other end to said mechanism and acting in the opposite direction whereby ambient temperatures are compensated, a source oi. energy, a heating element controlling said first heat responsive element, a circuit connecting said source and said heating element to urge said mechanism in one direction, a second heating element controlling said second heat responsive element, and a second circuit connecting said source, said second heating element and said 

